John Ackermann N8UR wrote:
There hasn't been much discussion on the list about this idea. I know that Timing Solutions (now Symmetricom) used to make -- or at least advertise -- a "clean-up oscillator" that was a very low noise, very high short-term stability BVA oscillator that would lock to your Cesium reference. With a proper time constant (10s of kseconds?), that should give the best of both worlds with superlative short term performance and atomic long-term stability.
The math is simple and clear on this and it works well. A pure clean-up oscillator may infact have higher bandwidth/lower tau to reduce the effects of the loop itself, just as any other "step up" oscillator. When running the phase comparator at the output frequency or low division rate of it, a fairly high bandwidth is possible which allows a much simplified locking loop for a fairly good result. Using a mixer and active loop will work very well too.
If possible, keep the comparator frequency fairly high and avoid charge-pump detectors (according to my experience with cheaper-tronic onces where dead-band created low rate wanderings while simple designs excelled in stability).
Using a low phase-noise oscillator for cleanup is a wise idea, even if no frequency multiplication occurs. Active loop PI-regulation of sufficient bandwidth suppresses most of frequency trackings of the oscillator, so long-term stability is less of an issue where as phase-noise plots are.
Cheers, Magnus _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
